It is common in transport refrigeration systems, such as transport refrigeration systems for use in trucks, trailers, containers, and the like, to drive a refrigerant compressor with an internal combustion engine, such as a diesel engine. It is also common to operate the engine at one of first and second engine speeds, such as 1400 RPM and 2200 RPM, called low speed and high speed, according to a temperature control algorithm. The engine is started at low speed, and as soon as it reaches low speed operation, the temperature control algorithm takes over, switching the engine to high speed, if required by the temperature control algorithm. The engine may be operated continuously, switching between cooling and heating modes to hold a selected set point temperature in a served space, or the engine may be operated in a start-stop mode, being stopped in a predetermined NULL temperature band adjacent to the selected set point temperature. During initial temperature pull down the temperature control algorithm normally operates the engine at high speed, in a high speed cool mode, and the engine speed is switched to low speed when the temperature of the served space has been dropped to a predetermined point adjacent to the selected set point temperature. The engine will then be operated in low speed cooling and heating modes, unless the ambient is at a temperature extreme which moves the temperature of the served space out of the low speed operating ranges to high speed cool or high speed heat portions of the temperature control algorithm.
An internal combustion engine in a transport refrigeration application is thus subjected to severe starting and stopping duty, especially when a start-stop temperature control algorithm is in control of the transport refrigeration system. Transport refrigeration systems must be highly reliable because they condition costly loads over-the-road where maintenance is not always quickly available. Thus, it would be desirable, and it is an object of the present invention, to reduce maintenance and prolong the useful operating life of the internal combustion engine in a transport refrigeration application.